Khakeran Valley, Afghanistan ? Skimming low over the desert in helicopters with guns at the ready, American troops advanced Sunday into southern Afghanistan, seeking to reassert control after a spate of attacks raised fears of an Iraqi-style insurgency here.

The troops hopped from village to village in Khakeran Valley, searching mud huts and wheat fields, meeting village elders and detaining at least two men.

Up to 300 insurgents are believed to be holed up in the valley, about 130 miles northeast of the main southern city of Kandahar, said Lt. Luke Langer, a platoon leader in the 503rd Infantry Regiment, 173rd Airborne Brigade.

“The enemy has been using the Khakeran Valley as a sanctuary,” he said. “Without question, I know the Taliban are in the area, and I’m sure we will make contact. From talking to local people, we know the enemy are very angry with us being here.”

About 465 suspected insurgents have been reported killed since the start of a major upsurge in March, when snows melted on mountain tracks used by the militants. In the same period, 29 U.S. troops, 38 Afghan troops and 125 civilians have been killed.

Blistering U.S. assaults against nearby mountainous camps last week left 178 suspected militants dead.

Flying in a convoy of two CH-47 Chinook helicopters, a Black Hawk and two Apache attack choppers, about 50 American troops moved up the river valley from village to village, searching for militants.

The biggest loss for the insurgents was in the three-day barrage by American aircraft against rebel camps in Miana Shien district, Kandahar province, last week. While about 80 militants, including two top Taliban commanders, are still believed to be in the area, dozens of others are believed to have fled.

American spokesman Lt. Col. Jerry O’Hara said troops were operating across the whole region, “taking away enemy sanctuaries.”

“The enemy forces are not dumb. So when they get a sense that we’re doing an operation in area ‘X,’ they will move onto area ‘Y,”‘ he said. “It is our goal to be in area ‘Y’ before they set anything up.”